Voice over internet protocol (“VoIP”) communication systems allow the user of a device, such as a personal computer, to make calls across a computer network such as the Internet. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long distance calls. To use VoIP, the user must install and execute client software on their device. The client software provides the VoIP connections as well as other functions such as registration and authentication. Advantageously, in addition to voice communication, the client may also provide video calling and instant messaging (“IM”).
One type of VoIP communication system uses a peer-to-peer (“P2P”) topology built on proprietary protocols. To access the peer-to-peer system, the user must execute P2P client software provided by a P2P software provider on their PC, and register with the P2P system. When the user registers with the P2P system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the P2P system without the further use of a server. In particular, the users can establish their own communication routes through the P2P system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the P2P system. The exchange of the digital certificates between users provides proof of the user's identities and that they are suitably authorised and authenticated in the P2P system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a P2P system are disclosed in WO 2005/009019.
As mentioned, one advantage of VoIP communication systems is the ability to support video calling. With video calling, the callers are able to view video images of the other party in addition to voice information. This obviously enables much more natural communication between the parties, as facial expressions are also communicated, thereby making video calls more comparable to a face-to-face conversation.
Traditional public switched telephone networks generally do not offer video calling functionality to users. High data rate mobile networks, such as 3rd generation (“3G”) mobile networks may offer video calling, but this generally expensive to the user. VoIP video calling is, by contrast, of very low cost or free to the user.
The visual aspect of a VoIP video call enables it to be utilised to display to remote party something that could otherwise only be described verbally, or would require a photograph to be taken and sent to the other party separately. An example of this is a new baby, who can be shown to relatives (some of which may live a long distance away) using video calling.
Therefore, a video call, which comprises a sequence of frames, may contain images that the called party may wish to keep (e.g. an image of the new baby, from the example above). There is therefore a need for a technique to capture and manage images from a video call stream in an efficient and user-friendly manner.